Device-to-device (D2D) communication mainly indicates D2D unicast communication or D2D broadcast/multicast communication. In a D2D unicast communications system, a device directly communicates with only another device. In a D2D broadcast/multicast communications system, a device simultaneously sends a data packet of the device to multiple devices near the device.
In the D2D broadcast/multicast communications system, D2D communication in the Long Term Evolution (LTE) is used as an example. FIG. 1 is a schematic diagram of a common D2D transmission manner. As shown in FIG. 1, a scheduling assignment (SA) is transmitted in an SA resource pool, and data is transmitted in a data resource pool. The SA resource pool and the data resource pool are separated in a time domain. For example, after transmission begins, the SA is transmitted first for two times, and then the data is transmitted for four times. The SA of a transmit end includes a time resource pattern of transmission that indicates a location at which the data is transmitted each time in the time domain, further includes resource assignments (RA) that indicate a location at which the data is transmitted for the first time in a frequency domain, and includes frequency hopping indication information indicating whether frequency hopping occurs in the frequency domain during the four transmissions. A receive end needs to correctly receive the SA in the SA resource pool first, can determine a location in the frequency domain for last three transmissions according to a frequency domain location for the first transmission and the frequency hopping indication information, then receives the data on a corresponding time-frequency domain resource in the data resource pool according to the time-frequency domain location information indicated by the SA, and then performs decoding or joint processing on obtained data transmitted each time to obtain the data packet. That is, the receive end can obtain the data packet of the transmit end only when little interference is imposed on the SA and the data.
Because the SA and the data packet are separately transmitted, the data packet can be obtained only when both the SA and the data packet are successfully transmitted. However, both the SA and the data packet may fail to be transmitted or may be transmitted with an error because of a transmission collision, half duplexing, in-band leakage, or the like, thereby causing relatively low transmission reliability of D2D communication.